Funds are requested to purchase a BIAcore 3000 surface plasmon resonance (SPR) spectrometer that will permit a group of 5 investigators to initiate new types of experiments probing the affinity and kinetics of macromolecular interactions in the complex cellular processes of transmembrane signaling, protein trafficking to organelles, maturation and degradation of proteins, chaperone-assisted protein folding, and transcription. These are multi-step processes in which the kinetics and affinity of macromolecule interactions are temporally regulated. Since the requested instrument can measure the kinetics of association and dissociation between macromolecules in a general and label-free manner, new experiments that are key to understanding the molecular mechanisms of these cellular processes can be conducted. The SPR approach is currently unavailable at the applicant organization, since there are no commercial instruments at the University of Massachusetts Amherst Campus, or at neighboring institutions in western Massachusetts. In addition to the major users on the proposal (R. Weis, L. Gierasch, D. Hebert, C. Martin, D. Schnell), minor users will have access to the instrument under the supervision of an instrument manager, a Ph.D.-level scientist employee of the University. The instrument will be placed in a shared instrument/computer facility of the Chemistry-Biology Interface Training Program, in which the major users are members, and will be supported through a user-based fee system, to cover instrument maintenance and operation costs. The instrument will serve a critical need in the biological and chemical research community at UMass by introducing a general and highly sensitive method for rapidly assessing macromolecular interactions at several levels, including: (1) yes/no binding interaction studies, (2) rank ordering of interaction affinities and the rates constants for association (and dissociation), (3) binding capacity, and (4) absolute estimates of the affinity and rate constants for these interactions. The sample-recovery feature of the Model 3000 can be put to effective use with the mass spectrometers in the University Mass Spectrometer and Molecular Weight Characterization Facility.